U.S. patent number 4,536,661 [Application Number 06/619,157] was granted by the patent office on 1985-08-20 for position-sensing apparatus.
This patent grant is currently assigned to Renishaw plc. Invention is credited to David R. McMurtry.
United States Patent |
4,536,661 |
McMurtry |
August 20, 1985 |
Position-sensing apparatus
Abstract
A machine tool spindle (10), rotatable in a housing (11), is
adapted to receive, as an alternative to a cutting tool, a probe
(12) having a stylus (14) whereby to sense a workpiece (15) for the
purpose of measuring it. On sensing the workpiece (15) the probe
(12) generates a signal which is transmitted to a fixed location
(X) on the housing (11). The probe (12) has a body (13) secured to
the spindle (10) for rotation therewith, such rotation being
required for certain measuring manouvres. To cope with the
transmission of the signal (17) from the rotating probe (12) to the
fixed location (X), the signal (17) is transmitted through the
intermediary of a sleeve (19) supported on the probe body (13) such
that the body (13) can rotate while the sleeve (19) is held still
by an axially disengageable mechanical connector (21) connecting
the sleeve (19) to the housing (11). The transmission of the signal
(17) takes place through a rotation-accommodating first inductive
coupling (28) between the probe body (13) and the sleeve (19), and
by a rotationally fixed but axially disengageable second inductive
coupling (30) between the sleeve (19) and the housing (11). The
probe and sleeve assembly (12,19) is connectable to and
disconnectable from the spindle (10) by a transfer mechanism (24).
The connector (21) and the second coupling (30) are engaged and
disengaged accordingly. The assembly (12,19) may include a duct
(31) for transmission of a cleaning fluid from the housing (11) to
the sensing end (14A) of the stylus (14).
Inventors: |
McMurtry; David R.
(Wotton-Under-Edge, GB2) |
Assignee: |
Renishaw plc
(Wotton-Under-Edge, GB2)
|
Family
ID: |
10533646 |
Appl.
No.: |
06/619,157 |
Filed: |
June 8, 1984 |
PCT
Filed: |
October 17, 1983 |
PCT No.: |
PCT/GB83/00263 |
371
Date: |
June 08, 1984 |
102(e)
Date: |
June 08, 1984 |
PCT
Pub. No.: |
WO84/01621 |
PCT
Pub. Date: |
April 26, 1984 |
Foreign Application Priority Data
|
|
|
|
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Oct 15, 1982 [GB] |
|
|
8229594 |
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Current U.S.
Class: |
307/119; 33/561;
33/832 |
Current CPC
Class: |
B23Q
1/0009 (20130101); G01B 7/012 (20130101); G01B
7/002 (20130101); G05B 2219/50252 (20130101); G05B
2219/37207 (20130101) |
Current International
Class: |
B23Q
1/00 (20060101); G01B 7/00 (20060101); G01B
7/012 (20060101); G01B 7/008 (20060101); G01B
007/02 (); G01B 007/12 () |
Field of
Search: |
;307/119,120,121,122
;33/174L,169C,172D,172E ;340/568,669,672,686 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
German Laid-Open Offenlegungsschrift 2 042 506 published Mar. 2nd,
1982. .
British Patent Specification 819,417 published Sep. 2nd,
1959..
|
Primary Examiner: Pellinen; A. D.
Assistant Examiner: DeBoer; Todd E.
Attorney, Agent or Firm: Spencer & Frank
Claims
I claim:
1. Position-sensing apparatus comprising a spindle (10) having an
axis of rotation (10A), a support structure (11) supporting the
spindle (10) for rotation, a probe (12) having a body (13)
releasably secured to the spindle (10) for rotation therewith, the
probe (12) further having means (14) for sensing an object (15),
means (26) for generating a signal (17) responsive to such sensing,
and external transmission means (30) for transmitting the signal
(17) from said body (13) to a locaton (X) provided on said support
structure (11) at a given angular position about said axis (10A),
characterised by a sleeve (19) supported on said body (13) for
relative rotation therebetween about said axis but against relative
axial movement, connector means (21) connecting said sleeve (19) to
said support structure (11) against rotation relative thereto but
allowing axial release therefrom together with release of said body
(13) from said spindle (10), internal transmission means (28) for
transmission of said signal (17) between said body (13) and said
sleeve (19) while accommodating relative rotation therebetween, and
wherein said external transmission means (30) is arranged for
transmission of said signal (17) between said sleeve (19) and said
location (X).
2. Apparatus according to claim 1 wherein said internal
transmission means (28) comprises a coupling (28) having a first
coupling element (28A) provided on one of said body (13) and said
sleeve (19) and adapted to cooperate with a circumferentially
continuous second coupling element (28B) provided on the other one
of said body (13) and said sleeve (19) for transmission of said
signal (17) so that on relative rotation of said body (13) and said
sleeve (19) transmission is maintained between said elements
(28A,28B).
3. Apparatus according to claim 1 wherein said connector means (21)
comprises a mechanical connector (21) having axially engageable and
disengageable connector elements (21A,21B) provided respectively on
said sleeve (19) and on said support structure (11).
4. Apparatus according to claim 3 wherein said external
transmission means (30) comprises a coupling (30) having first and
second coupling elements (30A,30B) provided at the respective
elements (21A,21B) of said mechanical connector (21).
5. Apparatus according to claim 1 wherein said probe (12) includes
a stylus (24) extending from said body (13) and having a
work-contacting end (24A), said sleeve (19) includes a fluid flow
duct (31), a fluid flow connector means (32) is provided between
said sleeve (19) and said support structure (11) for transmitting
fluid from said support structure (11) to said duct (31), and said
duct (31) has an outlet (31C) directed onto sad work-contacting end
(24A).
6. Apparatus according to claim 1 wherein said connector means (21)
comprises a mechanical connector (21) having axially engageable and
disengageable connector elements (21A,21B) provided respectively on
said sleeve (19) and on said support structure (11), and a fluid
flow connector means (32) comprises fluid flow connector elements
(32A,32B) provided at said elements (21A,21B) of the mechanical
connector (21).
7. Apparatus according to claim 5 wherein said fluid flow duct (31)
comprises a shroud (33) surrounding said stylus (14) at a part
(14B) thereof adjacent said body (13), and said outlet opening
(31C) extends around said part (14B) and is directed toward said
work-contacting end (14A) of the stylus (14).
Description
BACKGROUND OF THE INVENTION
This invention relates to position-sensing apparatus. It is known,
e.g. in numerically controlled machine tools, to provide a spindle
having an axis of rotation, a support structure supporting the
spindle for rotation, a probe having a body secured to the spindle
for rotation therewith about said axis, the probe further having
means for sensing an object, means for generating a signal
responsive to such sensing, and external transmission means for
transmitting the signal from said body to a location provided on
said support structure at a given angular position about said axis.
Said angular position is so selected that the external transmission
means does not foul other equipment present on the support
structure. However, it is often desirable to rotate the probe by
rotating the spindle, e.g. for the purpose of a particular
measuring manouvre. In the past such rotation was not possible
because of the selected angular position of said location.
BRIEF SUMMARY OF THE INVENTION
The present invention overcomes the above difficulty by the
provision of a sleeve supported on said body for relative rotation
therebetween about said axis but against relative axial movement,
connector means connecting said sleeve to said support structure
against rotation relative thereto but allowing axial release
therefrom together with release of said body from said spindle,
internal transmission means for transmission of said signal between
said body and said sleeve while accommodating relative rotation
therebetween, and wherein said external transmission means is
arranged for transmission of said signal between said sleeve and
said location.
BRIEF DESCRIPTION OF THE DRAWING
A preferred embodiment of the invention is described in detail, and
by way of example, hereinbelow with reference to the accompanying
drawing wherein:-
FIG. 1 is a sectional elevation of the tool spindle of a
numerically controlled machine tool,
FIG. 2 is a section on the line II-II in FIG. 1, and
FIG. 3 is a part view in the direction of the arrow III in FIG.
1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The spindle, denoted 10, is mounted for rotation about its axis 10A
in a stationary support structure or bearing housing 11. As an
alternative to the usual cutting tool, the spindle 10 has secured
thereto a position-sensing probe 12 having a probe body 13
supporting a stylus 14 whereby to engage a workpiece 15 for the
purpose of sensing the position thereof. The workpiece 15 is
supported on a table 16 which is measurably movable relative to the
spindle 10. The probe is adapted to output a probe signal 17
responsive to engagement between the stylus and the workpiece
during movement of the table 16. The probe signal 17 has to be
transmitted to the bearing housing 11 for further transmission to a
control system (not shown) adapted to determine the position of the
table, and thus of the workpiece, at the instant of the probe
signal 17. The probe 12 is connected to the spindle 10 by a taper
member 18 and is removable from the spindle 10 in the direction of
the axis 10A.
A sleeve 19 supported on the probe body 13 includes a radial arm 20
connected to the housing 11 by an axially releasable mechanical
connector 21 comprising an axially directed first element 21A
provided on the arm 20 and a second element or recess 21B provided
on the housing 11 for engagement by the element 21A. The connector
21 supports the sleeve 19 against rotation but permits axial
withdrawal of the sleeve 19 from the housing 11. The probe body 13
has a journal 22 on which the sleeve 19 is supported in a manner
permitting rotation of the body 13 about the axis 10A while the
sleeve 19 stands still. Shoulders 23, 23A on the body 13 prevent
axial motion of the sleeve 19 relative thereto. The sleeve 19 has
an annular groove 24 for engagement of the probe by a tool
mechanism 25 whereby the probe and sleeve assembly 12, 19 can be
axially removed from or inserted into its position on the spindle
10. The arm 20 is so positioned relative to a drive key 18A on the
taper member 18 that when the probe is inserted into the spindle by
the mechanism 25 the element 21A registers with the recess 21B.
The probe signal 17 is generated by the breaking of electric
contacts 26 when, on engagement between the stylus 24 and the
workpiece 15, the stylus is displaced by a small amount relative to
the probe body 13. The contacts 26 are arranged in an electric
circuit 27 connected to an internal transmission means defined by a
first inductive coupling provided between the body 13 and the
sleeve 19. The coupling 28 has a first coil 28A mounted
circumferentially locally on the body 13 and a circumferentially
continuous coil 28B mounted on the sleeve 19 so that the signal is
transmittable by the coupling 28 regardless of the relative angular
position of the body 13 and the sleeve 19. The diameter of the coil
28B is determined by the relatively small diametral dimension of
the body 13 and it therefore does not interfere with surrounding
structure. For transmission of the signal 17 between the sleeve 19
and the housing 11 there is provided an external transmission means
defined by a second coupling 30 situated at the outside of the
housing 11 and comprising two local coils 30A, 30B provided
respectively at the elements 21A, 21B of the connector 21.
The connector 21 and the coupling 30 are situated at a selected
angular location X about the axis 10A while permitting rotation of
the probe body 13 relative to the housing 11. If the arm 20 were
secured to the body 13, the arm 20 would inevitably participate in
the rotation of the body 13 and the coupling 30 would require a
circumferentially continuous coil, such as the coil 28B, provided
on the housing 11. This would require space which is not often
available at the adjacent end of the housing 11. This problem
arises especially in machine tools which are designed originally
for the use of tools only and where the probe facility is
introduced at a later stage as a so-called "retrofit" and, it will
be clear, the invention overcomes this difficulty. In a
modification, not illustrated, the inductive coupling 28 is
replaced by a slip ring coupling. In a further modification, not
illustrated, the inductive coupling 30 is replaced by an
opto-electronic coupling.
The probe and sleeve assembly 12,19 may include a fluid flow duct
31 leading from a fluid flow supply tube 34 mounted on the housing
11 to an opening 31C annularly surrounding the stylus 24 at a part
24B thereof adjacent the body 13. The opening 31C is directed along
the stylus 14 toward a work-contacting end 14A thereof. Fluid such
as compressed air or a liquid tool coolant is supplied to the duct
31 to be directed onto the end 14A of the stylus 14 to keep the end
14A clean. The duct 31 is provided on the sleeve 19 and comprises a
duct portion 31A in the arm 20 connected to the supply tube 34 by a
fluid flow connector 32 having a socket 32A provided on the element
21A and engaged by a plug 32B provided at the element 21B. The duct
portion 31A leads to a shroud 33 secured to the sleeve 19 and
surrounding the body 13. A clearance 31B between the body 13 and
the shroud 33 forms part of the duct 31 and leads to the outlet
opening 31C.
Preferably the element 21B of the connector 21 and the element 30B
of the coupling 30 are embodied in a mounting member 29 adapted to
be secured to the housing at the location X by screws 29A. Thus,
when a matching not having a probing facility is to be equipped
with such a facility, it is merely necessary to supply the mounting
member 29 along with the assembly 12,19. The latter assembly is
connectable to the spindle 10 by means of the taper member 18, or
an equivalent means, in the same way as the usual cutting tools,
and the mounting member 29 is readily secured to the housing 11 by
a simple fitting operation.
* * * * *